There are certain types of applications for switches and other electrical devices, as well as mechanical devices such as hydraulic valves, in which the switch or other device is enclosed within a housing and is operated by a movable handle or lever from outside of the housing. The device within the housing may be connected to a motor or other electrical load and it is commonly important, for safety and other reasons, to be sure that the switch is not operated inadvertently or by a person who does not understand why it is in the position which it occupies.
For this reason, switch actuators are sometimes provided with a locking capability which permits the switch to be locked in one or more of its operative positions, typically either on or off.